Friday, 11 November 2011

Hayfever (allergic rhinitis) time

I love it when the spring winds die away and the warm days of summer arrive. But I hate it too, because when Dactylis glomerata flowers, my life becomes miserable. I'm allergic to its pollen, and a bit less so to the pollen of a bunch of other grasses and wind-pollinated trees and herbs: oaks, chenopods, and plantains.

Cocksfoot, Dactylis glomerata, Wellington, NZ.

Dactylis glomerata, or cocksfoot, is a major pasture grass and weed in New Zealand. Its pollen is abundant from early November until the first week of January (I'm a walking bioassay) and again with a minor peak in March. In 1990, we bought a house in Okuti Valley, Banks Peninsula (this one), only to discover after we'd moved in that this valley used to be the cocksfoot seed growing centre of the known universe. It was Hell.

My first hayfever attack happened when I was about 9 or 10. My brother and I were playing outside with toy bombs that carried percussion caps, which exploded when you dropped them. (Fifteen years after WW2, these military toys were still very popular.) So we both reported in with itchy eyes and the parents assumed it was to do with the gunpowder in the caps. They called the doctor—doctors used to visit, on Saturday afternoons too, in those days— and we were sent to rest in darkened rooms. It was some time later they realized it was hayfever.

The TV advertisements for hayfever remedies always feature showy flowers: lilies, daisies and the like. But hayfever is an affliction caused by the insignificant flowers, the ones that are wind pollinated. Wind pollinated flowers have a rather haphazard method of dispersing their pollen; it's random and inefficient and so they need to produce a huge number of pollen grains for every ovule. They're insignificant because they don't need to attract a pollinator with showy petals and scents. But they fill the air with their pollen and it gets up our noses.

Insect- and bird-pollinated flowers have a much more efficient mechanism for dispersing their pollen, one that delivers it reliably to another flower. Because it's so much more efficient, they don't need to produce so much pollen, and it's not out there in huge amounts causing misery to folks like me.

You might think I'd hate all grasses. I have to admit I don't find them very interesting. But I do like this genus, Briza:

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About Me

(c) text and photographs copyright Phil Garnock-Jones and may not be used without permission.
I'm a botanist in New Zealand. Twitter handle: @Theobrominated. Retired from academia and now working part time as a researcher in plant taxonomy. The rest of my time I like to do the things on the list below.
You can ask if you want to use my photos in publications. For good causes, conservation and the like, I'll generally allow it without a fee; for commercial use, I'm likely to ask for a fee.